linux/arch/powerpc/kernel/dma.c

/*
 * Copyright (C) 2006 Benjamin Herrenschmidt, IBM Corporation
 *
 * Provide default implementations of the DMA mapping callbacks for
 * directly mapped busses.
 */

#include <linux/device.h>
#include <linux/dma-mapping.h>
#include <asm/bug.h>
#include <asm/abs_addr.h>

/*
 * Generic direct DMA implementation
 *
 * This implementation supports a per-device offset that can be applied if
 * the address at which memory is visible to devices is not 0. Platform code
 * can set archdata.dma_data to an unsigned long holding the offset. By
 * default the offset is zero.
 */

static unsigned long get_dma_direct_offset(struct device *dev)
{
	return (unsigned long)dev->archdata.dma_data;
}

static void *dma_direct_alloc_coherent(struct device *dev, size_t size,
				       dma_addr_t *dma_handle, gfp_t flag)
{
	struct page *page;
	void *ret;
	int node = dev_to_node(dev);

	page = alloc_pages_node(node, flag, get_order(size));
	if (page == NULL)
		return NULL;
	ret = page_address(page);
	memset(ret, 0, size);
	*dma_handle = virt_to_abs(ret) + get_dma_direct_offset(dev);

	return ret;
}

static void dma_direct_free_coherent(struct device *dev, size_t size,
				     void *vaddr, dma_addr_t dma_handle)
{
	free_pages((unsigned long)vaddr, get_order(size));
}

static dma_addr_t dma_direct_map_single(struct device *dev, void *ptr,
					size_t size,
					enum dma_data_direction direction,
					struct dma_attrs *attrs)
{
	return virt_to_abs(ptr) + get_dma_direct_offset(dev);
}

static void dma_direct_unmap_single(struct device *dev, dma_addr_t dma_addr,
				    size_t size,
				    enum dma_data_direction direction,
				    struct dma_attrs *attrs)
{
}

static int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl,
			     int nents, enum dma_data_direction direction,
			     struct dma_attrs *attrs)
{
	struct scatterlist *sg;
	int i;

	for_each_sg(sgl, sg, nents, i) {
		sg->dma_address = sg_phys(sg) + get_dma_direct_offset(dev);
		sg->dma_length = sg->length;
	}

	return nents;
}

static void dma_direct_unmap_sg(struct device *dev, struct scatterlist *sg,
				int nents, enum dma_data_direction direction,
				struct dma_attrs *attrs)
{
}

static int dma_direct_dma_supported(struct device *dev, u64 mask)
{
	/* Could be improved to check for memory though it better be
	 * done via some global so platforms can set the limit in case
	 * they have limited DMA windows
	 */
	return mask >= DMA_32BIT_MASK;
}

struct dma_mapping_ops dma_direct_ops = {
	.alloc_coherent	= dma_direct_alloc_coherent,
	.free_coherent	= dma_direct_free_coherent,
	.map_single	= dma_direct_map_single,
	.unmap_single	= dma_direct_unmap_single,
	.map_sg		= dma_direct_map_sg,
	.unmap_sg	= dma_direct_unmap_sg,
	.dma_supported	= dma_direct_dma_supported,
};
EXPORT_SYMBOL(dma_direct_ops);